Bumetanide and furosemide inhibited vascular endothelial cell proliferation

In this study, we examined the role of the bumetanide-sensitive Na+/K+/Cl-cotransport in the mitogenic signal of vascular endothelial cell proliferation. The activity of the Na+/K+/Cl- cotransport is dramatically decreased in quiescent subconfluent cells, as compared to subconfluent cells growing in the presence of FGF. The Na+/K+/Cl- cotransport activity of quiescent subconfluent cultures deprived of FGF decreased to 6%, whereas that of quiescent cells grown to confluency was reduced to only 33% of the activity of subconfluent cells growing in the presence of FGF. The basal low activity of Na+/K+/Cl- cotransport in the quiescent subconfluent vascular endothelial cells was dramatically stimulated by FGF. In order to explore the role of the Na+/K+/Cl- cotransport in the mitogenic signal of the endothelial cells, the effect of two specific inhibitors of the cotransport -furosemide and -bumetanide was tested on cell proliferation induced by FGF. Bumetanide and furosemide inhibited synchronized cell proliferation measured by direct counting of cells and by DNA synthesis. Inhibition by furosemide and bumetanide was reversible; removal of these compounds completely released the cells to proliferate. These results indicate that the effect of these drugs is specific and is not due to an indirect toxic effect. This study clearly demonstrates that the FGF-induced activation of the Na+/K+/Cl- cotransport plays a role in the mitogenic signal pathway of vascular endothelial cells.